Pelletized feeds are produced by hydrothermal treatment of a raw grain composition and processing the resulting mash. Typically the raw grain composition is processed in a conditioner where it is contacted and blended with steam injected into the conditioner with resultant gelatinization of at least a portion of the starch in the grain and formation of a heated, hydrated mash. The mash is delivered from the conditioner to a pellet mill where it is pressed through dies to form feed pellets. Typical industrial conditioners include steam treatment chamber and a series of blades that are attached to a rotatable tool bar mounted in the chamber. The blades are oriented on the tool bar to mix the grain composition with the injected steam and to advance the in-process grain composition through the conditioner. The tool bar is typically rotated at a high rate, often about 200 to 400 revolutions per minute. In practice, however, the raw grain composition is not uniformly processed (hydrothermally heated) because it is forced through the conditioner before the steam can be thoroughly blended with and penetrate the particulate constituents of the grain composition. The starch component in the pelletted product produced in such method is often insufficiently or not uniformly gelatinized resulting in poor quality feed pellets.
The present invention provides a method and apparatus for the improved manufacture of pelletized feeds. In one embodiment of the present invention there is provided an improved conditioner for hydrothermally processing a grain composition. The conditioner comprises a housing having a inlet end, an outlet end and a chamber positioned between the two ends. The conditioner includes a rotatable tool bar and first and second sets of radially extending blades, said blades positioned oriented to promote formation of a plug of in-process grain composition in the conditioner as a result of rotation of the tool bar during operation of the condition.
In one embodiment each blade in the first set of blades is oriented to lie in a first inclined position relative to the tool bar so that each blade in the first set of blades has a negative slope when viewed from a point away from the tool bar looking at the tip end of the blade. Each blade of the second set of blades is oriented to lie in a second inclined position relative to the tool bar so that each blade has a positive slope when viewed from a point away from the tool bar looking at the tip end of the blade. The tool bar is rotated during conditioner operation so that the first set of blades tends to advance the in-process grain composition from the inlet and toward the outlet end and the second set of blades tends to push the in-process grain composition toward the inlet end. The number and length of the blades in the first and second sets of blades can be variable as can the magnitude of the respective positive and negative slope inclinations of the blades within each set. Of course, the relative slope orientations of the first and second sets of blades can be reversed and the tool bar can be rotated in the opposite direction to provide an equivalent plug-forming effect.
The rate of rotation of the tool bar can be controlled/varied during conditioner operation to control plug formation and in-conditioner retention time of the grain composition. Raw grain composition is fed into the inlet end of the conditioner substantially continuously during conditioner operation and at variable controlled rate, and steam is continuously introduced into the conditioner chamber to process the grain composition as it is advanced through the conditioner by the action of the tool bar. Formation of the "plug" of the in-process grain composition in the conditioner chamber helps prevent the injected steam from escaping through the outlet end of the conditioner and improves efficiency of steam utilization in the process.
In one embodiment the first set of blades is positioned on the tool bar in an upstream region of the conditioner chamber near the inlet end, and the second set of blades is positioned on the tool bar in a downstream region of the interior chamber between the first set of blades and the outlet end. The plug-maker tool bar is coupled to a variable speed drive that can be controlled to rotate the tool bar at a defined speed/rotation rate within a range of speeds.
In another embodiment of the present invention, there is provided a method for increasing the rate of hydrothermal processing of a raw grain composition in a conditioner having a grain inlet, a grain outlet, an interior chamber positioned to lie between the grain inlet and grain outlet, a tool bar mounted for rotation in the interior chamber, a grain feeder for advancing the raw grain composition through the grain inlet and into the chamber, and a steam inlet for injecting steam into the interior chamber to contact the raw grain composition. The method comprises the steps of advancing the grain composition through the grain inlet and into the interior chamber of the conditioner, injecting steam into the interior chamber to contact the grain composition, forming a plug comprising the in-process grain composition in the chamber with negatively sloping blades and positively sloping blades coupled to the tool bar by continuously rotating the tool bar, continuing to inject steam into the chamber to complete the hydrothermal processing of the in-process grain composition as it is retained in the chamber as part of the plug, discharging portions of the processed grain composition in the plug through the chamber outlet, and substantially continuously replacing discharged portions of processed grain composition by delivering raw grain composition into the interior chamber through the inlet.
The present invention, therefore, comprises a conditioning chamber with an inlet and outlet end and a rotary blade assembly for advancing a grain composition from the inlet end to the outlet end. The blade assembly has blades at different pitches and/or locations to build a plug mass of grain in the composition chamber into which steam is injected to effect hydrothermal processing preliminary to pelletization of the composition. The blades are configured so that as the blade assembly is rotated at selected speeds, the grain composition is advanced from the inlet end of the chamber into the chamber to form part of the plug mass and ultimately through the outlet end of the chamber with the dwell time of the composition in the plug mass being sufficient to allow complete/effective hydrothermal processing of the composition to form a fluidized grain mash ideally suited for pellet milling.